1. Field of the Invention
The present invention relates to an image forming apparatus utilizing an electrophotographic process or an electrostatic recording process such as a copying apparatus, a printer or a facsimile apparatus, and more particularly an image forming apparatus provided with an opening and closing device which is opened or closed with respect to a main body of the apparatus.
2. Description of Related Art
A prior image forming apparatus particularly utilizing an electrophotographic process is often provided with a process cartridge integrally including a photosensitive member serving as an image bearing member and image forming device, such as a developing apparatus for interaction therewith, or a unit containing consumables to be replaced or replenished by a user, such as a transfer material container (sheet cassette) containing a transfer material such as a paper sheet for image formation. Also various proposals have been made for improving the operability of the replacement of the process cartridge or of the paper replenishment for the sheet cassette.
For example, Japanese Patent Application Laid-open No. H8-115042 discloses a structure in which attach-detach apertures for a unit for an image bearing member and a cassette for a recording medium are positioned on a same side of the main body of the image forming apparatus and have the same attach-detach direction.
Such a conventional structure, however, is a lateral-opening type of apparatus in which a front cover is opened about a vertical axis (hinge) and the front cover is merely supported at the hinge side, so that it is difficult to maintain the same positional precision of the front cover, to the main body of the apparatus, at left and at right (hinged side and opposite side).
Particularly in case an image forming device is mounted on the front cover, the positional precision becomes different at the left and the right sides of the image forming apparatus, thus hindering a satisfactory image formation operation.
Thus, Japanese Patent Application Laid-open No. H6-110262 discloses an apparatus in which a front cover is opened downwards about a horizontal axis (vertical-opening type) for the replacement of a process unit. Such an apparatus allows the maintenance of the same positional precision at the left and the right of the front cover.
It is described that, in such apparatus, a sheet cassette can be mounted and detached from the front side of the apparatus, but a device which determines an open position of the front cover is not described, and the replacement of the process unit is made possible but the replacement of the sheet cassette may be hindered depending upon the open position of the front cover.
Also Japanese Patent Application Laid-open Nos. H8-22157 and 2001-356550 describe an apparatus of the vertical-opening type, but does not describe a device which positions the open/closing member (cover) by determining a certain open position for the open/closing member (cover).
In a full-color image forming apparatus, there are provided with a plurality of process cartridges each having a photosensitive member for respective colors, and an improvement in the maintenance property because of an increased frequency of replacements. Also the presence of plural process cartridges tends to increase the dimension of the apparatus, and there is desired an apparatus capable of suppressing an increase in the dimension thereof even with an improved maintenance property.